The HRC7013 (first built in 1993) is the oldest, and generally speaking, the older the unit, the more likely parts will be discontinued or No Longer Available. For example, the carburetor for the original HRC7013 is discontinued.

-Robert@Honda

Caveat: I work for Honda, but the preceding was my opinion alone.

I was looking at a 36" HRC7113TXA and the owner said it was hydrostatic drive. Did that version have optional drive systems? Is the HRC7113TXA a fixed height deck? Are parts for that model obsolete?
Thanks in advance. Have a great day!